@media screen and (max-width: 768px) {
    /*写css代码  满足条件生效*/
    .medium {
        display: block;
    }
    .large {
        display: none;
    }
}

@media screen and (max-width: 992px) and (min-width: 768px) {
    .medium {
        display: block;
    }
    .large {
        display: none;
    }
}

@media screen and (max-width: 1200px) and (min-width: 992px) {
    .medium {
        display: block;
    }
    .large {
        display: none;
    }
}


@media (min-width: 1200px) {
    .medium {
        display: none;
    }
    .large {
        display: block;
    }
}